Telephone system



Aug. 3 1926.

w; T. POWELL TELEPHONE SYSTEM F'iLed June 6,

- 1924 2 Sheets-Sheet .1

INVENTOR WINFREDT. POWELL BY 9 ATTORNEY YMMV TmNv

rmmq 38 A33 .Aug. 3,1926. Y 1,594,690

W. T. POWELL TELEPHONE SYSTEM Filed n 6, 1924 2- Sheet-Sheet 2 TO OFFICE. EELECTOR swlrcH 14 TD ex INVENTOR WIN-REP T. POWE L.L

BY nay/14W.

d] ATTORblEY Patented An 3, i926.

tsetse UNITED stares entrant ()FFECEQ W'INFRED '1. POWELL, ()F ROCHESTER, NEY'V YGRK, ASSIGNOR TO THE STEOMBERG- CARLSON TELEPHONE MA NUFACTUEEETG CORPORATION OF NEW YORK.

GGIVLFANY, OI RGGHES'IEB, NEVIYORK, A

TELEPHONE SYSTEM.

Application filed June 6,

This invention relates to telephone systems and more particularly to telephone systems employing automatic switches in completing 'ie portion of a telephone connection. in telephone systems the length of telephone lines and line characteristics vary t with the result that unless suitable is i V rovidcd speech transmission is tar trom in term.

It is the purpose of the present invention to provide novel means tcr rendering certain the characteristics of all the telephone lines of a 9;roup uniform so that standard etliciency of transmission ma be maintained.

Other features will appear from the detailed description and appended claims.

The drawings with Fig. 1 placed above Fig. 2, diagrammatically represent the invention which be incorporated in telephone systems now in use. Fig. 2 represents a trunk circuit terminating in a selector switch, indicated at the right of the figure. portion of the dra ing at the left of the dotted line of Fig. 2 together with Fig. 1 represent the means which may be associated with the tr nk circuit of Fig. 2 and which may be adjusted to render the characteristics of a portion of telephone connection of a predetermined value. In the lower part of Fig. 1 there is shown a selector switch for seizing an idle one of a plurality of testing devices. Fig.1 3 shows a schematic arrangement to indicate the means for testing whether or not the condition for uniform transmission has been established in the telephone connection. 7

For convenience in description and disclosure it is assumed that the present invention is incorporated into a large sized telephone system of the type disclosed in the patent to Lundell #1 l93 861, granted January 17, 1922. In that patent it is shown that a callinn telephone line is extended to a wanted telephone line through a district selector switch, an otlice selector switcln an incoming selector switch and a final selector switch. These switches are variably and selectively controlled by register sender and its asso-v ciated controlling means The present invention has been incorporated in the mentioned systemin the income ing selector itch shown in Fig. 10 of the inentionedpatent. which has been modified to nicl'udeitlie present i ention bat he e 1924. Serial No. 718,210.

possible the same reference characters used in the patent have been retained.

It is believed. unnecessary to disclose and describe in detail how a calling line is extended through a district switch and an oiiice switch to the mentioned incoming selector, but it has been assumed. that the calling line has been extended in the manner de scribed in the patent and that the incoming" selector switch has been operated to connect the trunk, whose conductors are designated 900 and 901, to the trunk Whose conductors are rsterred to as 7 and i8 leading to a final selector switch, which is then operated to seize the wanted line. The method of operating the incoming selector is now well known in this art and it is sufficient to state that when the trunk leading to the final selector has been seized and when the final selector switch has been operated, the sequence switch 913 is standing in position 15.

The circuits are now in condition for applying ringing current of theproper character to signal the wanted station on the called line and in the event that this line is a party line, the selection of the proper ringing current is determined by the position of the sequence switch 913. If it is stopped in position 15 rinsing current of one character is applied to the called line and if this sequence switch is stopped in position 16, the

relay 10 energized to apply ringing cur rent of another character;

in position 15 of the sequence switch 913, a circuit is closed from grounded battery through the lower contact of sequence switch spring 909, the outer armature and back contact of relay 903 the left hand armature and heel: contact of relay 923, the lower right hand and upper left hand contacts of sequence switch spring 912, the armature and. back contact of relay 950, back contact and inner armatureott relay 941, winding of relay 938 the continuity spring and back contact of relay 948, sequence switch contact 949, conduct-or 900 and thence to ground at a preceding switch in the series The operation of the relayr938 closes circuit from ground at the inner armature and front contact of this relay, continuity springand back contact of relay 12, windingof relayld to grounded battery. This circuit operates the relay '13 and extends the last descri ed circuit through th pper" most armature and front contact of relay 13, armature, back contact and Winding of motor magnet 14, resistance, to grounded battery. Under the control of this circuit the motor magnet 14; advances the brushes 15, 16, 17, 18, 11,19-and 20 0f the selector switch until an idle testing network is seized. lVhen such an idle netork is found, a circuit is closed from ground at the armature and back. contact of relay 21 bruslr19, left hand Winding of relay 12, inner armature and front contact of relay 13, through the resistance to grounded battery. This last circuit is effective to energize relay- 12 and to stop the operation of the motor magnet 14. As soon as relay 12 is operated, it closes a lockingcircuit for itself, from grounded battery, Winding of relay 2 1, selector brush 20, high resistance Winding of the relay 12, the armature and continuity. spring of this relay, inner front contact and armature of relay 9 238 to ground. enteritis the circuit of relay 10 through the selector brush 11 and the innermost armature and front contact of relay 12, to he sequ nce it h ontac 1 and ifgthe sequence switch 913 is standing in position 16, the mentioned relay 10 is operated to apply ringing currentfrom the source designated 22. If, however, the sequence switch is standing in position 15, relay 10 is not-operated and ringing. current from the source 23 is applied to the called line.

The operation .ofthe relay 938 opens the trunkcond-uctors 900 and 901 leading back to the register sender, (not shown), thereby causing the register sender and its ass0- ciated controlling mechanism to be restored to common use as is described in th mentioned patent.

With the relay 12 operated a circuit is closed from ground at contact 24 of the swit hho kt t l ed bs a n v r the lower side of thecalled line and through the final selector switch (not shown), trunk condnctor Y, selector brushfieb, conductor 25, armature and contact 26, of relay 1.2, brush 16, Winding of the relay 2?, back contact and armature of relay 28, through the right hand contacts and armature of relay 21 in multiple, through resistance C, to grounded battei'y and through resistance D, to ground. Atthe' armature and contactSl of relay 12, a branch circuit in mutinle of that just described is extended over conductor 32, brush 3 in any 9 of it Pos t ns, t g h resistance unit suc a A, condu o uppermost armature and. front contact of re ay. .3 c9 1d1'19t i35;' 9 t was tuna '.e 3 71" 1 351 1 11 5 38, i i a tur eandbackcontact o gfitb gifoundlecirc utnist described vith ewe ts e e be The ,lVhe-atstone bridge circuit just described is established as soon as the called line is selected. It Will be further noted that the resistance designated L in Fig. 3 is the one side of the called line, Whiclris also indicated by the symbol L in Fig. 2. In order for the relay 27 to be inactive the ratio of the resistance arms'A/C and L/D must be equal. If this bridge is not properly balanced, relay 27 is energized and closes an operating circuitfor the motor magnet 37 from grounded battery, its Winding, armature and back contact, contact 38 and armature of relay l2, selector brush 15, front contact and armature of relay 27,'to ground. Under the control of this circuit the motor magnet 37 advances its brushes 33, 39 and 40, until a sufficient number ofthe resistance units A are introduced into the lVheatstone bridge, so that it is'balan'ced and the relay 2? deenergizes. Atthat time the motor magnet 37 stops the Selector brushes to preserve the established balance.

It is believed that the operation of the compensator Will best beunderstood by referring to specificconditions, For example, if the predetermined value of the loop resistance of all the lines is to be 400 ohms, the compensator brush 40 must advance until it includes a suiiicient number of the resistance units B, so that the sum of these resistance units and the resistance-of the upper side of the called line equals 200 ohms, that is, one halfof the predetermined resistance. The resist.- auce units B rendered effective by the coinpensator brush 4&0, are included in the called end of the circuit traversed by the voice currents, so that it is necessary to connect in the lower side L, of the called line, the, same amount of resistance units A, in order to establish abalanced line condition. Battery is connected to one terminal of the A resistance units, While the circuits are in the condition for signaling the called line and when the circuits are completed forconversation, the A resistance units are connected in this talking circuit. Thus .the A resistance units serve the double purpose of act ing as an arm of thelVheatstone' bridge for testing the line after which a sufiicie nt number of these units are connectedin the called line o stabl shi g a anced line n i tion.

Let it now be assumed that the linecalled has a loop resistance oflQO ohms in which caseeach side-of the called line isequivalent toaresistance of. 5Qoh1ns] The resistance coils and ofFig. 1 are constant and for purposes of this descriptionfit illbe jasited t a co l 0 hi ara i o '2 Qlifi aafon ajvalue of 25 oh luibugn it w n he understood that fthesefcoils. may have smattering; of-Va'lucs ordert 'v'e aeriqqeaer i: are.

of the arms of the 'Wheatstone bridge arrangement should be such that L/D A/G or 50/25:;1/25. Since it has been assumed that L equals 50 ohms, D equals 25 ohms and C equals 25 ohms, therefore, a sufficient number of the A resistance units must be included in the circuit to equal 50 ohms. From this itwill be seen that to render the upper side of the called line of the same value as the lower side of the called line plus the. B resistance units, the complement of the value of 50 ohms, that is 20050 or 150 ohms must be included in the called line.

As a further illustration assume that the called line has a total loop resistance of 50 ohms. In this case each side of the called line is equal to 25 ohms. In this instance the ratio A/CrzL/D becomes A/25 25/25, which means that the A resistance units included in the testing circuit' must equa ohms. But one side of the calling line has a resistance of 25 ohms and to bring this resistance up to the predetermined amount of 200 ohms, 17 5 ohms of resistance A must be included in the talking circuit.

It shouldbe noted that from the above mentioned examples, two conditions must be satisfied by the compensator circuit. First, the VVhe-atstone bridge testing condition, where the A resistance must increase as the line resistance increases and second, the condition arising from the fact that the called line must have a predetermined loop resistance, so that in the talking condition the A resistance must decrease as the line resistance increases. In Fig. 2 it is shown that the value of A increases as the switch brush 33 moves in a clock-wise direction, therefore, when the line resistance is large, the A resistance must be increased by the movement of the brush 33. 7

During the talking condition, compensator brush becomes effective and brush. 33 is disabled. The contacts engaged by the switch brush 39 are so connected to the resistance units A, that as the brush 39 moves in a clock-wise direction, the value of these resistance units in, the circuit decreases and during the talking condition, relay 12 is deenergized, so that brush 39 becomes effective. From this arrangement one group of resistance units is used for testing and a complement of this number is used in the talking circuit.

In order to insure that a sufficient interval of time is allowed for the compensator to take its setting, after the called line is selected relays 40 and ll are provided. When the relay 21 is operated as previously ex plained, a circuit is extended from ground at the left hand armature and front contact of relay 21, winding of relay 41, back contact and armature of relay 40 and to grounded battery, whenever the contacts .42 of the common interr pter closed. The opera armature and front contact it closes an opcrating circuit for relay 28 and this last named relay on operation closes a locking circuit for itself, through its upper front contact and armature, left hand front contact and armature of relay 21 to ground.

it hen the called party answers the relay 950 cperat d which effects the deenergization of relay 938, which in turn releases the relay 12. The release of the last named re lay restores the common testing circuit for use in other connections.

At'the close ofthe conversation the release of the operated equipment takeslplace in the well known manner.

What I claim is 1. In a telephone systenntelephone lines, means including a link circuit for intercom necting a pair of telephone lines, means for compensating for variations in one of said telephone lines of a connection, and means including a testing net-work common to a pli'irality of link circuits for controlling the operation of said compensating means.

2. In a telephone system, a plurality of telephone lines having varying electrical characteristics, means including link circuits for interconnecting said telephone lines in. pairs, compensating units for rendering of a predetermined value. certain of the characteristics of a telephone line of a connection, a plurality of networks common to said link circuits for determining the number of units to be actively associated with said telephone connection, and means including an automatic switch for selecting an idle net-work.

3. In a telephone system, a plurality of telephone lines of varying electrical values, means including link circuits for interconnecting said telephone lines in pairs, means for rendering the characteristics of a called telephone line of a predetermined value, and means controlled over one side only of a telephone line for controlling said means.

i. In a telephone system, a plurality of telephone lines, of varying electrical characteristics, means including link circuits for interconnecting said telephone lines in pairs, a plurality of electrical units arranged tri be associated with one of the telephone lines of a connection for rendering said line equal to a predetermined value, and means including a testing arrangement controlled over said last mentioned telephone line for measuring the electrical va e of said. line and for connecting electrical units therein equal to the complement of the value of the tested telephone line,

5. In a telephone system, a plurality of telephone lines of varying electrical characteristics, means including link circuits for interconnecting saidtelephone lines in pairs, a plurality of unlts arranged to be associated with one o'i-the telephone l nes of a connection for rendering said tele-- switches and link circuits for interconnect-v ing said telephone linesin pairs, a plurality oi' units arranged to be associated with one of the telephone lines of a connection for rendering said telephone line equal to a predetermined value, a plurality of common mechanisms including a testing arrangement controlled over said last mentioned telephone line for measuring the electrical value of said line and for connecting electrical units therein equal to the complement of the value of the tested telephone line, and automatic means for associating an idle mechanism with a telephone connection.

7. In a telephone system, a plurality of telephone lines each provided with a ringer, means including link circuits for interconnecting said telephone lines in pairs, signaling equipment, circuits through which said signaling equipment is connected to a link circuit extended to the ringer ot'a called telephone line of an interconnected pair of lines, means including a progressively movable switch tor selecting and completing an idle circuit to said signaling equipment, and means for disconnecting. said; signaling equipment from said link circuitbetore said first mentioned interconnection is terminated. 1

8. In a telephone system, a plurality of telephone lines each provided with a ringer,

means including automatic switches and link circuits for interconnecting said tele phone lines, signaling equipment, circuits through which said signaling equipment is connected to a link circuit extendedto the ringer of a called telephone line of an interconnected pair, means including apro gressively movable switch for seleciing and completing an idle connecting circuit, and means for disconnecting said signaling equipment from said link circuit before said first mentioned interconnection is terminated. i

9. In a telephone system, a plurality of telephone lines, means including a link circuit for interconnecting a pair of telephone lines, means for compensating for varia tions in one of said telephone lines of a connection, means including, a testing network common to a plurality of link circuits for controlling the operation of said compensating means, a source of ringing current, and means including an automatic switch for seizing said testin net-work when idle for connecting said source of ringing current to said link circuit.

10. In a telephone system, telephone lines, means including a link circuit for interconnecting a pair of telephone lines, means for compensating for variations in one of said telephone lines of a connection, and a lVheatstone bridge arrangement for controlling the operation of said compensating means, said lVheatstone bridge 'arrangen'ient including a testing network common to a plurality of link circuits.

11. In a telephone system, a plurality of telephone lines having varying electrical characteristics, means including link circuits for interconnecting said telephone lines in pairs, compensating units for rendering of a predetermined value, certain of the characteristics of a telephone line of a connection, a lVheatstone bridge arrangement for determining the number of units to be ac tively associated with said telephone connection, said \Vheatstone. bridge arrangement including one of a plurality of net Works common to said link circuits, and

means including an automatic switch for associating, an idle network with the link circuit of a connection. 1

In witness whereof,- I hereunto subscribe my name this 4th day of June A. D. 1924.

, WVINFRED T. 

